Study On Fe-based Alloy Powders For The Laser Cladding And The Rapid Forming

Laser rapid forming(LRF)is a new and advanced manufacturing technology that has been developed on the basis of high power laser cladding technology and rapid prototyping.Most of the laser cladding and laser rapid forming materials are as the same of conventional applied techniques.In order to explore the potential application value of laser surface strengthening,new kind of cladding material needs to be developed.The processing research is the base of the laser cladding and rapid forming.First, we studied the effects of laser processing parameters such as laser power,scan speed, track overlap,Z axis increment,powder sending rate on the dimension and quality of forming samples.The optimal technologic parameters were powder sending rate: 10g/min;laser power:1400-1500W;scan velocity:5mm/s;spot diameter:3mm; overlap rate:50%;Z axis increment:0.3mm.Secondly,according to the forming materials design principle and the characteristic of materials used as laser cladding on the market,we confirmed the constitutes of the forming materials by and large.The effects of Y₂O₃ on microstructure,phase,wear-resistance of the laser cladding and rapid forming parts were also studied.The study shows that Y₂O₃ can make the microstructure finer,more uniform,improving the wear-resistance and appearance;but the excessive addition of Y₂O₃ can make microstructure coarser,reduce the wear-resistance and cause the prototyping part to warp and crack.And we confirmed the constitutes of the laser rapid forming materials.In the end,we studied the technic guideline of Fe-based powders alloy for the laser cladding and the laser rapid forming:First,the hardness of the cladding layers could surpass HRC32.Second,using tribological wear experiment machine,it has been found that the mass loss of the laser rapid forming part and the substrate is 116.5mg and 3802.9mg respectively.The wear-resistance of the laser rapid forming part is higher than that of the substrate.Third,the ultimate strength of laser rapid forming part is 675MPa.The end,without any preheating and slow cooling,a cylinder of laser rapid prototyping(wall thickness 2mm,height 40mm,outside diameter 30mm)can be made with a smooth surface and without gas holes and crack.In situ synthesized TiC reinforced Fe based coating was fabricated by laser cladding on steel substrate using Fe-based alloy and TiO₂+C as the precursor powders. The phase composition and microstructure of the clad layer were investigated by means of X-ray diffraction analysis(XRD),scanning electron microscopy(SEM)and electron probe microanalysis(EPMA).Results showed that uniformly distributed TiC particles could be synthesized by the in situ reaction.The hardness and wear properties of the clad layer were greatly improved due to the presence of TiC particles in comparison with the substrate.